Field of the Invention
The present invention relates to a vibration-type actuator that drives a vibrating body in a combination of two bending vibration modes, and an electronic apparatus having the vibration-type actuator.
Description of the Related Art
There are known a variety of vibration-type actuators which bring a driven body into pressure contact with a vibrating body, which is constructed by joining an electro-mechanical energy conversion element such as a piezoelectric element to an elastic body, and move the vibrating body and the driven body relatively to each other through driving vibrations excited in the vibrating body. For such vibration-type actuators, a driving method using a combination of two bending vibration modes for exciting driving vibrations in the vibrating body is known.
Japanese Patent Publication No. 4261964 discloses a vibrating body that has a rectangular flat-shaped elastic body, a piezoelectric element joined to one surface of the elastic body, and two projecting portions provided with a predetermined space left therebetween in a longitudinal direction in a central part of the other surface of the elastic body in a lateral direction such that the two projecting portions project in a thickness direction of the elastic body. By applying voltage to the piezoelectric element, oval motions are generated in upper end faces of the projecting portions within a plane including both of the thickness direction and the longitudinal direction of the elastic body. Thus, by bringing the driven body and the upper end faces of the projecting portions into pressure contact with each other in the thickness direction of the elastic body, the vibrating body and the driven body are moved relatively to each other in the longitudinal direction of the elastic body (direction that connects the two projecting portions together).
Japanese Patent Publication No. 3363510 discloses a first vibrating body that has a rectangular flat-shaped elastic body, a piezoelectric element joined to one surface of the elastic body, and two prismatic projecting portions provided with a predetermined space left therebetween in a longitudinal direction in a central part of the other surface of the elastic body in a lateral direction such that the two projecting portions project in a thickness direction of the elastic body. By applying voltage to the piezoelectric element, oval motions are generated in upper end faces of the projecting portions within a plane including both of the thickness direction and the longitudinal direction of the elastic body (within a plane perpendicular to the lateral direction of the elastic body). Thus, by bringing the driven body into pressure contact with ends of surfaces of the projecting portions, which are perpendicular to the lateral direction of the elastic body, in the thickness direction of the elastic body, the first vibrating body and the driven body are moved relatively to each other in the longitudinal direction of the elastic body.
Japanese Patent Publication No. 3363510 also discloses a second vibrating body that has a rectangular flat-shaped elastic body, a piezoelectric element joined to one surface of the elastic body, and a total of four prismatic projecting portions each pair of which is provided with a predetermined space left therebetween in a longitudinal direction on each long side of the other surface of the elastic body. By applying voltage to the piezoelectric element, oval motions are generated in upper end faces of the projecting portions within a plane including both of the thickness direction and the longitudinal direction of the elastic body. Thus, by bringing the driven body into pressure contact with the upper end faces of the projecting portions, the second vibrating body and the driven body are moved relatively to each other in the longitudinal direction of the elastic body.
Japanese Laid-Open Patent Publication (Kokai) No. 2006-115559 discloses a vibrating body that has a rectangular flat-shaped elastic body, a piezoelectric element joined to one surface of the elastic body, and one projecting portion provided on the other surface of the elastic body such that the projecting portion projects in a thickness direction of the elastic body. By applying voltage to the piezoelectric element, an oval motion is generated in an upper end face of the projecting portion within a plane including both of the thickness direction and the longitudinal direction of the elastic body. Thus, by bringing the driven body into pressure contact with the upper end face of the projecting portion in the thickness direction of the elastic body, the vibrating body and the driven body are moved relatively to each other in the longitudinal direction of the elastic body.